A typical integrated GPS/INS system is depicted as FIG. 1. The GPS receiver and IMU are the two major parts in the integrated system. The GPS receiver receives RF signals from the GPS satellites while the IMU produces its own signals because of its self-contained characteristics. From the viewpoint of installed system testing, the simulation of a GPS receiver and an IMU is much different. Usually a real-time GPS satellite constellation RF simulator is used to generate the GPS satellite signals and inject them into the GPS receiver. But we cannot inject electronic signals into an IMU from outside.
A straightforward method for dynamic ground testing is the application of the flight motion tables that provide the motion of the aircraft or munitions during simulated flight in an installed system environment. With this method, the GPS receiver receives actual satellite RF signals and the IMU produces dynamic inertial measurement signals itself, for the integrated system is actually in motion. But this motion table method is not a viable solution. It needs a large set of testing equipment, its operational cost is high, its dynamic motion is limited, and its data acquisition during the simulation is not convenient. Therefore, the real-time computer simulation system for the dynamic ground testing of the installed system is desired.